The invention relates to a positioning device having a first and a second transport arm for alternately transferring plate-shaped objects from a storage position into an operational position which extends in a plane transverse to a Z-direction, whereby an object is placable in the operational position by means of the first transport arm after a further object has been taken from the operational position by means of the second transport arm.
The invention also relates to an optical lithographic device provided with a positioning device according to the invention.
A positioning device of the kind mentioned in the opening paragraph is known from Japanese Patent Application no. 62-195143. The known positioning device is used in an optical lithographic device for the manufacture of electric semiconductor circuits, a semiconductor circuit pattern provided on a mask being imaged on a semiconductor substrate. During this, the semiconductor substrate is illuminated through a number of different masks which are taken from a mask magazine one by one and positioned on a mask support of the optical lithographic device by the positioning device.
The known positioning device is provided with a first and a second transport arm which are displaceable along a first and along a second guide parallel to the first, which guides are provided on a turntable which is common to both transport arms. After a first mask has been placed in the operational position by means of the known positioning device, the turntable is rotated towards the mask magazine, after which a second mask is taken from the magazine by means of the first transport arm. Subsequently, the turntable is rotated back towards the mask support, and the first mask is taken from the operational position by the second transport arm, upon which the second mask is placed in the operational position by the first transport arm. Finally, the turntable is rotated towards the mask magazine again and the first mask is returned to the mask magazine by the second transport arm, after which the first transport arm is in a position to take a next mask from the mask magazine again.
A disadvantage of the known positioning device is that the first mask cannot be returned to the mask magazine until after the second mask has been placed in the operational position. As a result, the time duration required after placement of a mask in the operational position for taking a next mask from the mask magazine and putting it in readiness for exchange with the mask present in the operational position is increased, and the production output of the optical lithographic device in which the positioning device is used is adversely affected.